commit 841cff6e4fe1cdd370cd51019e69c6c564e8059c Author: George Kadianakis <desnacked@riseup.net> Date: Mon Sep 30 18:29:00 2019 +0300 Stop libevent from reading data from closed connections. Code adapted from Rob's proposed patch in #30344. Also add a comment in connection_mark_for_close_internal_() on why we should not be adding extra code there without a very good reason. --- changes/bug30344 | 4 ++++ src/core/mainloop/connection.c | 18 ++++++++++++------ src/core/mainloop/mainloop.c | 10 ++++++++++ 3 files changed, 26 insertions(+), 6 deletions(-) diff --git a/changes/bug30344 b/changes/bug30344 new file mode 100644 index 000000000..37561bf94 --- /dev/null +++ b/changes/bug30344 @@ -0,0 +1,4 @@ + o Minor bugfixes (connection): + - Avoid reading data from closed connections, which can cause needless + loops in libevent and infinite loops in Shadow. Fixes bug 30344; bugfix + on 0.1.1.1-alpha. diff --git a/src/core/mainloop/connection.c b/src/core/mainloop/connection.c index 2f03d919a..3595bba85 100644 --- a/src/core/mainloop/connection.c +++ b/src/core/mainloop/connection.c @@ -897,13 +897,19 @@ connection_mark_for_close_(connection_t *conn, int line, const char *file) } /** Mark <b>conn</b> to be closed next time we loop through - * conn_close_if_marked() in main.c; the _internal version bypasses the - * CONN_TYPE_OR checks; this should be called when you either are sure that - * if this is an or_connection_t the controlling channel has been notified - * (e.g. with connection_or_notify_error()), or you actually are the + * conn_close_if_marked() in main.c. + * + * This _internal version bypasses the CONN_TYPE_OR checks; this should be + * called when you either are sure that if this is an or_connection_t the + * controlling channel has been notified (e.g. with + * connection_or_notify_error()), or you actually are the * connection_or_close_for_error() or connection_or_close_normally() function. - * For all other cases, use connection_mark_and_flush() instead, which - * checks for or_connection_t properly, instead. See below. + * For all other cases, use connection_mark_and_flush() which checks for + * or_connection_t properly, instead. See below. + * + * We want to keep this function simple and quick, since it can be called from + * quite deep in the call chain, and hence it should avoid having side-effects + * that interfere with its callers view of the connection. */ MOCK_IMPL(void, connection_mark_for_close_internal_, (connection_t *conn, diff --git a/src/core/mainloop/mainloop.c b/src/core/mainloop/mainloop.c index 6e2b300fb..4b3c3bf6a 100644 --- a/src/core/mainloop/mainloop.c +++ b/src/core/mainloop/mainloop.c @@ -879,6 +879,16 @@ conn_read_callback(evutil_socket_t fd, short event, void *_conn) /* assert_connection_ok(conn, time(NULL)); */ + /* Handle marked for close connections early */ + if (conn->marked_for_close && connection_is_reading(conn)) { + /* Libevent says we can read, but we are marked for close so we will never + * try to read again. We will try to close the connection below inside of + * close_closeable_connections(), but let's make sure not to cause Libevent + * to spin on conn_read_callback() while we wait for the socket to let us + * flush to it.*/ + connection_stop_reading(conn); + } + if (connection_handle_read(conn) < 0) { if (!conn->marked_for_close) { #ifndef _WIN32